BACKGROUND: Active Crohn's disease can be treated using liquid diet therapy (LDT), but non-adherence may limit success, necessitating corticosteroid therapy. Whole-protein polymeric formula (PF) seems to be much more palatable than amino acid-based elemental formula (EF) and thus may significantly improve adherence to LDT. AIM: To compare adherence to LDT using PF versus EF. METHODS: Success in completing a 6-week course of LDT, need for nasogastric tube administration of formula and use of LDT for relapses were compared between children presenting with active disease and treated with EF (n = 53) and children given PF (n = 45). RESULTS: Remission rates were similar (EF 64%, 95% CI 51 to 77 vs PF 51%, 95% CI 37 to 66; p>0.15). 72% (95% CI 60 to 84) given EF completed the initial course of LDT compared with 58% (95% CI 44 to 72) given PF (p = 0.15). Of those failing to complete the initial course, 13% on EF and 16% on PF gave up by choice (non-adherence), the remainder stopping due to treatment failure. Nasogastric administration was more frequent with EF (55%, 95% CI 42 to 68) compared to PF (31%, 95% CI 17 to 45) (p = 0.02). Among those treated successfully at first presentation, LDT was used for 28% of relapses in the EF group (95% CI 12 to 44) and 39% in the PF group (95% CI 19 to 59) (p>0.2) over the next year. CONCLUSION: PF did not effect adherence to LDT but was associated with significantly reduced need for nasogastric tube administration of formula.